[Qgis-user] Number of vertices

[Nyall Dawson]

On 24 April 2017 at 11:52, Martin Bain <Martin.Bain at lismore.nsw.gov.au> wrote:
> Hi Anke,
>
> The asPolyline() function of a geometry returns a list of points.  You can
> then simply get the length of the list:
>
>
>
>
>
> lyr=iface.activeLayer()
>
> sel=lyr.selectedFeatures()
>
> obj=sel[0].geometry()
>
> verts=obj.asPolyline()
>
> print verts
>
> [(526002,6.81305e+06), (526011,6.81309e+06), (526016,6.81311e+06)]
>
>
>
> print len(verts)
>
> 3

While this will work, it's quite slow as it requires copying all the
geometry's points into a new list. A faster approach is:

feature.geometry().geometry().nCoordinates()

In case you're wondering, the extra ".geometry()" gives you access to
the QgsAbstractGeometry interface containing all the low level methods
for working with geometry primitives.

Nyall


>
>
>
> Cheers,
>
> Martin.
>
>
>
> From: Qgis-user [mailto:qgis-user-bounces at lists.osgeo.org] On Behalf Of Anke
> zur Gölden
> Sent: Sunday, 23 April 2017 4:39 PM
> To: QGIS User List <qgis-user at lists.osgeo.org>
> Subject: [Qgis-user] Number of vertices
>
>
>
> Good morning
>
>
>
> is there a way to get the number of vertices for a Polyline?
>
> I am looking for the python method to get if possible
>
>
>
> thx
>
> Anke
>
>
>
>
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